1. Field of the Invention
The invention relates to mounting of gas turbine engine composite airfoils and, particularly, for mounting the airfoils in aircraft gas turbine engines.
2. Description of Related Art
Bypass gas turbine engines of the turbofan type generally includes a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. The core engine includes a high pressure compressor, a combustor, and a high pressure turbine in a serial flow relationship. The high pressure compressor and high pressure turbine of the core engine are interconnected by a high pressure shaft. The high pressure compressor, turbine, and shaft essentially form the high pressure rotor. The high pressure compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. The gas stream flows aft and passes through the high pressure turbine, rotatably driving it and the high pressure shaft which, in turn, rotatably drives the compressor.
The gas stream leaving the high pressure turbine is expanded through a second or low pressure turbine. The low pressure turbine rotatably drives the fan and booster compressor via a low pressure shaft, all of which form the low pressure rotor. The low pressure shaft extends through the high pressure rotor. The fan is part of a fan section of the engine and further includes a fan casing surrounding the fan and supported by a fan frame. Typically, a fan frame includes structural fan struts radially extending across a fan bypass duct. A forward vertical support mount on the fan casing is used to pivotably join and support the engine to a pylon on the aircraft and a thrust mount on the frame located radially inwardly of the bypass duct is used to transfer thrust loads of the engine to the aircraft through the pylon.
The frame may further include fan outlet guide vanes circumferentially distributed between the struts that are used to straighten fan airflow exiting the bypass duct. The fan struts and outlet guide vanes are typically made of metal which are heavier than available composite materials. Outlet guide vane assemblies are used to remove swirl before a fan nozzle at the end of a bypass duct. Such outlet guide vane assemblies are configured to turn the airflow discharged from the fan to a substantially axial direction prior to the fan flow being channeled through the bypass duct. In addition to turning the fan airflow, the outlet guide vane assembly also provides structural stiffness to the fan frame.
It is very desirable to incorporate composite materials in the engine in order to lower the weight of the engine which provides a more fuel efficient engine and aircraft. It is known to manufacture aircraft gas turbine engine vane airfoils from composite materials. What is further desired are mounting systems for securely and robustly mounting composite airfoils in the fan frame assembly that will enhance the life of the airfoils and fan frame assembly.
Vanes incorporating composite airfoils especially ones that are structural vanes, must transfer loads from the composite airfoil to metallic support structure such as the fan frame. In addition to being structurally sound it is important for the vane to be low in weight. It is important to transfer the load from the composite airfoil to the metallic airfoil support structure and to the rest of the fan frame with minimal weight impact.